Recently, RNA molecules in mammalian cells have been extensively studied, but their role in mitosis is not fully understood because of the mitotic repression of transcription, that is, the repression of transcripts from mitotic chromosomes. Several studies have identified the distribution and function of RNA molecules in mitosis; however, the relationships between RNA molecules and condensed chromosomes during mitosis have not been systematically studied. In this study, we investigated specific RNA molecules during mitosis and identified structural components that surround the chromosomes, called Mitotic Chromosome Coating Spheres (MiCCS), by using an in-cell deproteinization assay. Furthermore, we observed the unique distribution patterns of the RNA molecules in terms of mitotic chromosomes, MiCCS, mitotic cytoplasm, and outer membranes - of mitotic cells- by using a mitotic three-dimensional RNA fluorescent in situ hybridization (3D-RNA-FISH). These data provide us with a novel perspective of the relationships between RNA molecules and mitotic chromosomes.

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To evaluate cytogenetic validity of a simple vitrification technique for embryo cryopreservation, mouse 1-cell embryos were vitrified 4, 6, and 8 h after in vitro fertilization (IVF). In addition, chromosomal damage of spermatozoa treated with methyl methanesulfonate (MMS) was estimated using vitrified 1-cell embryos. More than 90% of embryos survived vitrification regardless of the time after IVF. In the 4-h and 6-h groups, some of the surviving embryos swelled after recovery. The incidence of structural chromosome aberrations and aneuploidy in embryos with morphologically normal features did not significantly increase in any group. The vitrification technique preserved 1-cell embryos derived from MMS-treated spermatozoa without alteration of chromosome damage. This technique will enable us to manage the optimal time for chromosome preparation of mouse 1-cell embryos.

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Karyotypes of four calliphorids, namely, Triceratopyga calliphoroides, Lucilia porphyrina, Chrysomya pinguis and Xenocalliphora hortona are described. The chromosome complement of T. calliphoroides and X. hortona is being described for the first time in the present communication. The chromosome complement of all the species comprises 2n=12, with five pairs of large euchromatic autosomes and a pair of heteromorphic sex chromosomes-XX in females and XY in males. The five autosomal pairs reveal a great deal of similarity in all the four species while the sex chromosomes show variation in size. Comparison of the karyotypes of these species with muscoid calyptrate Diptera reveal considerable similarity among autosomes and variation in sex chromosomes.

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